Enhanced Geothermal: Energy Holy Gail

Here is another bit of my upcoming book:Ten Technologies to Save the World – Kicking the Fossil Fuel Habit. The chapter on Geothermal includes geo-exchange (heating and cooling buildings), regular geothermal (tapping hot aquifers for electrical production) and EGS – Enhanced Geothermal Systems. EGS is the game-changer, and if pursued with vigor, could contribute in a huge way to getting us off oil. Here I describe what it is and ask: what do you get for a trillion dollars? Answer: you could replace 75% of U.S. electrical production.

Idea: Drill EGS holes beside every coal plant. Replace the boiler with a heat-exchanger. Keep the rest of the infrastructure. Turn off the furnace. Done.

In most of the world the ground 6 miles (10 km) underneath our feet is dry, but as hot as the hottest aquifer. That heat can be mined, brought to the surface, and used to generate electricity.

Enhanced Geothermal Systems (EGS) represent the great hope of geothermal, the holy grail of electrical production. Available around-the-clock, throughout the year, and available almost anywhere, it is suitable to be the workhorse of the world’s electrical system—with a constant baseload supply. It’s got colossal potential—the ground beneath the US could easily provide all its energy needs for the foreseeable future. EGS is the real deal.

How does it work? Drill down a long way—2.5 to 6 miles (4-10 km)—until you reach hot rock approaching 400 ˚F (200 ˚C). Drill another hole some distance away. Push water down the first hole at high pressure, creating a network of cracks between the two holes through which liquid can flow. Essentially, create a big, complex and very deep ‘geo-loop’. To mine the heat, pump liquid down one hole, let it seep through the cracks in the rock, and up the other. Grab the heat at the surface and use it to generate electricity. If you ever run out of heat, just move over a mile or two, start again, which will allow the first area to heat up again.

To get a sense of how much energy is stored in the ground, imagine a 70,000 metric ton pile of coal. Extracting enough heat to lower the temperature of a chunk of rock measuring 1/4 cubic mile in volume (1 cubic km) by just one degree, will give you as much energy as you get by burning that pile of coal. It could provide electricity to 14,000 homes for a year.[i] Ten degrees gets you 140,000 homes.

The real magic of EGS is you can drill for it pretty much anywhere. London, Adelaide, Toronto or New York, it doesn’t matter—we’re not limited to those few, thin veins of heat close to the surface.

Starting with experimental projects in the 1970s at Los Alamos National Laboratory, US, and at Cornwall, UK in the 1980’s, methods were developed to make fractures in hot, dry rock lying deep below the surface. A full-scale international collaboration is underway in Soultz, France. Small, experimental holes 2.2 miles (3.5 km) deep were drilled back in 1997, and the site has now been expanded to a full-scale pilot project using three holes 3.1 miles (5 km) deep. Water pumped into one hole emerges from the other at about 400 ˚F (200 ˚C). A power plant big enough to power 1500 homes is currently in operation.[ii]

Soultz is not the only project on the way. Drilling has started at two locations in Australia, one at Paralana, and a massive second project at Cooper Basin. There has been an operational plant in Landau, Germany since 2007 which produces enough power for more than 6000 homes. Sweden and Japan are also in on the action. The first commercial plant in the US, partly funded by the US Department of Energy, is planned for Desert Peak, Nevada.

MIT estimates that an EGS plant capable of powering 100,000 homes would take up less than a square mile (2 sq km), and use a 1.2 cubic mile (5 cubic km) underground reservoir of rock. When that plant runs out of heat—which would happen every 6 years or so—then you simply drill new holes a few miles away. The earth will gradually reheat the original area. This is truly renewable energy.

EGS is still in the early stages of commercial development, and there remain technical uncertainties—related to the geophysics of deep-earth rock fracturing, water flow and loss rates, for example—plus all sorts of engineering issues are sure to pop up. But these are ‘mere’ engineering problems, the sort of challenges engineers face all the time. Bob Potter, at 88 years of age, is one of those engineers.

Bob Potter was a co-founder of EGS while working at Los Alamos National Laboratories back in the 1950s. Not one to hang up his hat, just five years ago Mr. Potter founded Potter Drilling. Now backed with money from Google, he is working on (literally) cutting-edge technology to lower the cost of drilling those deep holes. Teamed up with his son, they’ve invented a new type of drilling technology that fractures the rock by spraying super-heated 1500 degree F (800 C) water out of a nozzle, instead of using traditional drill bits. They figure they can bring the cost of drilling down by half, and get it done faster. Drilling is a big part of the cost of EGS, and showing it can be done cheaply would go a long way to establishing commercial viability.

There is no real question about the long-term potential of EGS. That MIT report clearly established that there is more than enough accessible EGS energy to power the entire planet for thousands of years.

Trillion-Dollar Question:

What do you get for a trillion dollars? A trillion dollars worth of EGS? Around 400 GW of capacity,[iv] capable of filling three-quarters[v] of US electrical requirements.

[i] Assuming an average cost of $12,000 per household, spread across condos and homes. 83.3 million households get installed. There are approx. 105 million households in the US (Source: US Census Bureau)

[ii]. Approximately 70% of energy use is for heating/cooling (space and water). Geo-exchange lowers heating/cooling energy use by 75% (actual amount varies according to electrical source and original heating source). Total energy reduction would be 80% (portion of population) times 70% (heating/cooling portion) times 75% (energy savings) = 42% of total residential energy use

[iv] Costs of EGS are divided between exploration and drilling, construction of power plant, and present value of future re-drilling. There are two ways of generating an estimate:

First – assume cost of large-scale EGS to be similar to existing geothermal—the holes may be deeper, but EGS benefits from economies of scale, ease of site location, proximity to transmission and ongoing drilling technology improvements. Estimate: $1,057 (lowest cost – US EIA), $1,150-$3,000 (Renewable Energy Policy Project), $1,663 (MIT) per kW of capacity. Average = $1,600/kW of capacity.

Second– MIT estimates that 65% of the final cost of EGS electricity, per kWh, is due to carrying costs of initial capital investment (MIT Report, pg. 9-9), available at long-term average of around 8% (MIT Report, pg. 9-37). Breakeven price for EGS is around 6¢/kWh if deployed on a large scale (MIT Report, pg. 9-38). So capital carrying costs are ($0.65 times 6¢ = 3.9¢) per kWh. Assume 90% capacity factor: 1 kW of capacity generates 7884 kWh per year; capital carrying costs are (7884 kWh times 3.9¢) equals $307 per kW per year. Amortize this payment over 30 years and the up-front capital is $3,491 per kW.

Take the average of the two methods: approximately $2,500 per kW.

Therefore, a trillion dollars gets you 400 GW of capacity

[v] The US uses around 4 million GWh a year (US EIA)—400 GW, at 90% capacity, can produce more than 3 million GWh a year

[i] Average US household electrical use is around 11000 kWh per year (Source: http://www.eia.doe.gov/emeu/recs/recs2001/enduse2001/enduse2001.html). One metric ton of coal can provide approximately 2200 kWh (Source: US EIA; Approximately 2 billion MWh were produced from 1 billion US short tons of coal in 2007. That’s 2200 kWh per metric ton). Therefore 70,000 metric tons generates 154 million kWh or 14,000 house-hold years of electrical power

[ii] For a full, technical update on the Soultz project status at time of writing, see: http://pangea.stanford.edu/ERE/pdf/IGAstandard/SGW/2009/genter.pdf

>Hi Tom, you EGS technology idea seem great. Could turn out to be a real energy saver and help us wean ourselves off the reliance of gas. We in http://climatarians.org need to make a concerted effort to make the switch. With a little attitudinal change and more resolve, we can make it. Everyone should get together in the effort.